Roll Laminating Fiber Overlays on Low-Grade Ponderosa Pine–A Progress Report

Reports results of pilot plant tests with the roll-laminator to investigate the commercial feasibility of upgrading low-grade ponderosa pine lumber through the application of fiber overlays. The lower Common grades of ponderosa pine common to Arizona and New Mexico have been difficult to market profitably. Earlier cooperative studies involving the Forest Service and industry established the basic concepts, of using fiber overlays to mask defects and improve paintability. Development of a suitable roll-laminator and improved resins made it possible to pilot test the process. Lumber meeting overlay quality requirements can be satisfactorily overlaid with several types of overlays and adhesives at speeds up to 150 feet per minute. Production costs, based on 5-mil vulcanized fiber, applied to one face with wrapped edges, ranged between 4 and 5 cents per board foot, exclusive of the cost of lumber. The low proportion of lumber in the problem grades that meet overlay substrate requirements severely limits the application. Grade recovery studies at a number of representative mills show that only 24 percent of grade 3 Common, 8 percent of 4 Common, and zero percent of grade 5 Common lumber produced meet the requirements. Knotholes, unsound knots, and torn or pulled grain are the most serious defects and require development of suitable repair methods to make the process fully effective. Abrasive sanding and wood and chemical patching offer promise, and are being studied further. The report also includes tentative grade specifications for the lumber substrate. A marketing study conducted concurrently with the pilot test identified siding and molding as overlaid products that offered greatest opportunity.

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